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Any opinions expressed in this memoir are those of the author(s)and do not necessarily reflect the views of the

National Academy of Sciences.

H a r o l d c l a y t o n u r e y

1893—1981

A Biographical Memoir by

James r . arnold, JacoB BiG eleisen, a nd

clyde a . HutcHison, Jr .

Biographical Memoir

Copyright 1995NatioNal aCademies press

washiNgtoN d.C.

363

HAROLD CLAYTON UREY

April 29, 1893–January 5, 1981

B Y J A M E S R . A R N O L D , J A C O B B I G E L E I S E N , A N D

C L Y D E A . H U T C H I S O N J R .

HAROLD UREY WAS A SCIENTIST whose interests, accomplish-ments, and influence spanned the disciplines of chem-

istry, astronomy, astrophysics, geology, geophysics, and biol-ogy. Although he was meticulous in his attention to detail,his sights were always on broad questions at the forefrontof knowledge. His unusual powers of concentration andcapacity for hard work accounted for much of his successin exploring and opening up major new fields of research,including his discovery of deuterium and work on isotopechemistry, isotope separation, isotope geology, and cosmo-chemistry. Urey’s approach to a new area began with hisbecoming thoroughly familiar with what was known aboutthe subject of his curiosity and then the formulation of atheory to explain a large amount of uncorrelated material,which was then followed by carefully planned experiments.The latter frequently involved the design of new experi-mental equipment beyond the state of the art.

As a graduate student in physical chemistry in the early

A part of the section “Urey’s Personal Life and His Political and Educational Activi-ties” in this memoir is taken with permission of the publisher from Memoir 43, by C.A. Hutchison Jr., in Remembering the University of Chicago, Teachers, Scientists and Schol-ars, ed. E. Shils, copyright ©1991 by the University of Chicago. All rights reserved.

364 B I O G R A P H I C A L M E M O I R S

1920s, Urey realized that future progress in that disciplinewould require a knowledge of the quantum theory of atomicand molecular systems, which was undergoing a revolutionin Europe. He supplemented his command of mathematicsand physics by formal coursework prior to going to theBohr Institute in Copenhagen in 1923. His exposure thereled to his formulation of the concept of the electron spinconcurrent with but less complete than the Goudsmit-Uhlenbeck discovery. After completion of his text with ArthurRuark, Atoms, Quanta and Molecules, one of the first Englishtexts on quantum mechanics and its applications to atomicand molecular systems, Urey became interested in nuclearsystematics. This led to his discovery of deuterium. Theconception of this search, the design of the experiment,the actual discovery, and its publication are a model for theplanning and execution of scientific research. His discov-ery of the differences in the chemical and physical proper-ties of deuterium compounds led to his broader interest inisotope chemistry and isotope separation. Here again hedeveloped the theory that led to the prediction of the mag-nitude of isotope effects in the light elements. He followedthis up with experiments to confirm the theory, and thisled to his pilot plants that achieved the first concentrationof 15N, 13C, and 34S.

Urey’s interest in democratic government and world af-fairs led to the sense of urgency that developed in the Man-hattan Project late in 1941. His major contributions anddedication to the success of the program through his workon uranium isotope separation, heavy water production, and10B enrichment and his service on the various NRDC andOSRD committees related to the development of the atomicbomb have never been fully appreciated.

With the war behind him Urey conceived the isotopethermometer and its application to geochemistry. From there

365H A R O L D C L A Y T O N U R E Y

he became interested in the moon, formation of the plan-ets, meteorites, the abundances of the elements, and fi-nally, the origin of life. He was a major supporter of themanned mission to the moon and was an active investigatorin the program.

Harold Urey was a warm and generous person. He waswarm in all his personal relations and generous with histime, attention, and resources. To have known him andworked with him were unequaled experiences for each ofthe authors of this memoir. None of us could have pre-pared this memoir alone.

UREY’S EARLY LIFE UP TO HIS ENTRANCE TO

GRADUATE SCHOOL IN BERKELEY

Harold Clayton Urey was born in Walkerton, a small townin Indiana, on April 29, 1893. His father, a school teacherand a minister in the Church of the Brethren, died at thetime Harold was just starting his elementary schooling. Upongraduation from grade school at age fourteen, Urey barelymanaged to pass the entrance exams for high school. Butin high school he became interested in all aspects of hiswork, due, he said, to the excellent teachers he had there,and he immediately became the leader of his class in allsubjects, a position he maintained throughout his high schoolyears and in college.

When in 1911 at age eighteen he graduated from highschool, Urey became a teacher in a small country school inIndiana with some twenty-five children in various grades.After one year he went to Montana, where his mother, step-father, brother, and sisters had already gone, and taught insmall elementary schools.

It was while teaching in a mining camp that the son ofthe family with which he was living decided to attend col-lege, and this influenced Harold to do the same. He en-


tered the University of Montana in Missoula in the autumnof 1914. By carrying a heavy schedule of courses he wasable to complete his college education in three years with astraight A record, except in athletics. He did this in spite ofbeing required by his financial situation to wait on tables inthe girls’ dormitory and work one summer on the railroadbeing built there. Many years later in his Willard GibbsMedal address he spoke warmly of the inspiration he re-ceived from the professors at the University of Montanaand of the beginning of his interest in science due to theircounseling advice, in particular the influence of A. W. Bray,professor of biology. Under Bray’s guidance Harold ma-jored in biology, and his first research effort was a study ofthe protozoa in a backwater of the Missoula River. His in-terest in the origins of life, a field in which he was to makea major contribution much later at the University of Chi-cago, originated with that earliest research. Bray also en-couraged him to study chemistry, and he obtained a secondmajor in that subject.

World War I began as Urey entered the university, and atthe time he completed his work there in 1917 the UnitedStates declared war. He was urged by his professors to workin a chemical plant, chemists being badly needed at thattime. During the rest of the war he worked at the BarrettChemical Company in Philadelphia. In 1919 after the endof the war he returned to the University of Montana asinstructor in chemistry.

After two years of teaching he realized that if he was toadvance academically he would need to obtain a Ph.D. de-gree. The head of the Chemistry Department at Montanasent a letter of recommendation to Professor Gilbert N.Lewis of the Chemistry Department of the University ofCalifornia, Berkeley. A fellowship was offered to Harold,


and so in 1921, at the age of twenty-eight, he entered theUniversity of California as a graduate student.

FROM CHEMICAL PHYSICS TO ISOTOPE GEOLOGY

The educational facilities, opportunities, and philosophyof Berkeley’s Chemistry Department matched Urey’s inter-ests. The department stressed exploration of new ideasthrough original research and its weekly seminars. Therewere a minimum of formal requirements. Urey, neverthe-less, took the opportunity to enroll in courses in mathemat-ics and physics, which he deemed essential for his educa-tion as a chemist. In an unpublished autobiography (ca.1969), Urey described his two years as a graduate student as“among the most inspiring of any of my entire life.” Histhesis was self-generated. The first part was an outgrowth ofhis unsuccessful attempt to measure the thermal ionizationof cesium vapor. Bohr, Herzfeld, and Fowler had shownearlier that the ideal gas approximation leads to a dissocia-tion instability for an atom with an infinite number of statesbelow the dissociation or ionization limit. Its partition func-tion is infinite at all temperatures. Urey and later Fermishowed that the correction of the ideal gas approximationfor the excluded volume of the dissociating species leads toa convergence of the partition function of the atom or mol-ecule. Urey’s result was published in the Astrophysical Jour-nal. When he became interested in the moon and planets,Urey was wont to tell his younger astronomy colleagues thathe published a paper in the Astrophysical Journal before theyentered the field. The second part of his thesis was of lesserlong-term significance. He attempted to calculate the heatcapacities and entropies of polyatomic gases before the cor-rect description of the rotational energy states of moleculeshad been established by quantum mechanics.

When Urey received his doctorate in 1923, he realized


that there was much he needed to learn about the struc-ture of atoms and molecules. He received a fellowship fromthe American Scandinavian Foundation and went to theInstitute of Theoretical Physics, Bohr Institute, inCopenhagen. The institute under Bohr’s leadership was amajor center in theoretical physics, particularly the devel-opment of the new quantum mechanics and its applicationto atomic and molecular structure. There Urey became ac-quainted with Heisenberg, Kramers, Pauli, and Slater andthe biochemist Hevesy. Before Urey returned to the UnitedStates in 1924, he attended a meeting of the German Physi-cal Society where he met Einstein and James Franck, wholater became lifelong friends.

On his return to the United States Urey took a positionas associate in chemistry at Johns Hopkins University. Therehe continued his association with physicists, including Ames,Herzfeld, and Wood of Hopkins; Brickwedde, Foote, andMeggers of the Bureau of Standards; and Tuve of the CarnegieInstitution. His research at Hopkins ranged from specula-tions on the spin of the electron to cooperative experi-ments with F. O. Rice on the disproof of the radiation hy-pothesis of unimolecular reactions. With Arthur Ruark, Ureywrote Atoms, Quanta and Molecules. He had established him-self as one of the new generation of chemists who appliedthe new quantum mechanics of Heisenberg and Schrödingerto chemistry.

In the fall of 1929 Urey joined the Columbia faculty asassociate professor of chemistry. He initiated both experi-mental and theoretical research. In the former area hiswork was mainly in spectroscopy—ultraviolet spectra of tri-atomic molecules and vibrational spectroscopy. He and hisstudent Charles Bradley measured the Raman spectrum ofsilico-chloroform, a tetrahedral molecule. They found thatnone of the molecular force fields in use at the time could


reproduce the spectra of tetrahedral molecules. They intro-duced a new force field, the Urey-Bradley field, which is anadmixture of valence bond and central force fields. TheUrey-Bradley field remains in use in the analysis of the vi-brational spectra of tetrahedral molecules. Urey’s theoreti-cal work at that time was directed to nuclear stability andthe classification of atomic nuclei.

In 1931 Urey had on the wall of his office a chart ofatomic nuclei. On the ordinate his chart was labeled “pro-tons”; on the abscissa he plotted “nuclear electrons.” Thiswas prior to the discovery of the neutron. The number ofnuclear electrons is the number of neutrons in the nucleus.The atomic number or nuclear charge is the number ofprotons minus the number of nuclear electrons. For thelight elements Urey’s chart showed the stable nuclei 1

1H,42He, 6

3Li, 73Li, 9

4Be, 105B, and 11

5B. From nuclear systematics,Urey and others postulated the existence of 2

1H, 31H, and

52He. No isotopes of hydrogen or helium other than 11H and42He were known in 1931. From atomic weight consider-ations, to be discussed below, it was estimated that, if astable isotope of hydrogen of mass 2 existed, its naturalabundance would be less than 1:30,000 parts of 1

1H.

DISCOVERY OF DEUTERIUM

As early as 1919 Otto Stern reported an unsuccessful searchfor isotopes of hydrogen and oxygen, other than the onesof masses 1 and 16, respectively. In 1929 two Berkeley chem-ists, W. F. Giauque (who had been a graduate student con-temporary of Urey) and H. L. Johnston, discovered the stableisotopes of oxygen, 17O and 18O. Their natural abundancesare 0.04 and 0.2 percent, respectively. The chemical atomicweight scale was based on the assumption that oxygen hadonly one isotope, mass 16. The atomic weight of hydrogenwas based on the relative densities of hydrogen and oxygen


gases and the atomic weight of natural oxygen equal to 16.Aston had determined the atomic weight of hydrogen basedon 16

8 O = 16. The chemical value of the atomic weight ofhydrogen was 1.00777 ± 0.00002. Aston’s mass spectrographvalue, 1.00778 ± 0.00015, reduced to the chemical scaleusing the 1931 values for the abundances of 17O and 18Owas 1.00756. To reconcile the physical and chemical atomicweights of hydrogen, Birge and Menzel postulated the ex-istence of a stable isotope of hydrogen of mass 2 with anatural abundance of 1:4500.

Urey read Birge and Menzel’s communication in PhysicalReview in August 1931. Within days he decided to look foran isotope of hydrogen of mass 2 and outlined his plan ofattack. He would need a method of detection, and it wouldbe desirable to prepare samples enriched in this isotope.The design of the experiment was a model of how oneshould conduct a search for a small effect. It was the proto-type of the characteristics of Urey’s work for the next twodecades. As a method of detection, Urey and his assistantGeorge Murphy chose the atomic spectrum of hydrogen.An isotope of hydrogen of mass 2 should have red shiftedlines in the Balmer series. The shifts could be calculatedfrom the Rydberg formula for the energy levels in the hy-drogen atom after taking into account the relative massesof the electron and nucleus. They amounted to 1.1 to 1.8 Åin four lines in the visible part of the spectrum. Thesecould readily be resolved with the 21-foot grating spectrographthat had just been installed at the Pupin Laboratory of Co-lumbia University. The latter had a dispersion of 1.2 Å/millimeter in the second order. To enrich the heavy iso-tope, Urey and Murphy chose the distillation of liquid hy-drogen. They estimated the fractionation factor for 1

1H21H

from 11H2 in the range between the freezing and boiling

points from a Debye model for liquid hydrogen. Their esti-


mated fractionation factor was 2.5. To achieve an overallenrichment of 100 to 200 above natural abundance wouldrequire evaporating 5 liters of liquid hydrogen to 1 ml. Theheavy hydrogen should be in this 1-ml residue. There werebut two places in the United States capable of producing 5liters of liquid hydrogen in 1931. They were Giauque’s labo-ratory at the University of California and the low-tempera-ture laboratory at the National Bureau of Standards in Wash-ington, D.C. The NBS cryogenic laboratory had beenestablished by Hopkins physics graduate F. G. Brickwedde,who overlapped with Urey at Hopkins. It is not difficult tounderstand why Urey chose to collaborate with Brickwedde.

During the period when Brickwedde was preparing theenriched sample, Urey and Murphy determined the opti-mum conditions for excitation of the atomic spectrum ofhydrogen and suppression of the molecular spectrum. Theydid in fact find the lines to be expected for 2

1H in theatomic spectrum of natural hydrogen. They delayed publi-cation until these lines could be shown to increase in inten-sity in an enriched sample. In particular, it was necessary torule out any possibility that the 21H lines were artifacts (e.g.,“ghost” lines from periodic errors in the ruling of the grat-ing or lines from the molecular spectrum). The first ofBrickwedde’s samples showed no increase in the intensitiesof the lines attributed to 2

1H. A less persistent person thanUrey would have dropped the search. Brickwedde then pre-pared two more samples each by evaporation of a 4-literbatch of liquid hydrogen, this time close to the triple point,where the enrichment factor is somewhat larger than at thenormal boiling point. Spectroscopic examination of thesesamples on Thanksgiving Day of 1931 confirmed the dis-covery of hydrogen isotope of mass 2, subsequently nameddeuterium. Urey reported his success to his wife, Frieda,


when he returned to his home in Leonia, New Jersey, hourslate for Thanksgiving dinner.

For the discovery of deuterium, Harold Urey receivedthe Nobel Prize in chemistry in 1934. Urey was the thirdAmerican to receive a Nobel Prize in chemistry. He wasyoung in comparison with most Nobel laureates in chemis-try prior to or since 1934. He was the first of the Californiaschool to receive a Nobel Prize. He valued the contribu-tions that his associates made to the discovery for which hereceived the recognition and shared one-quarter of the prizemoney with F. G. Brickwedde and G. M. Murphy.

In Urey’s Nobel lecture, delivered on February 14, 1935,he called attention to the fact that Aston had just redeter-mined the physical atomic weight of hydrogen to be 1.0081.This value, if correct, would have brought the physical andchemical atomic weights of hydrogen into exact agreementand invalidated the basis of Birge and Menzel’s prediction.Urey would not have undertaken the search for deuteriumin 1931 and its discovery would have been delayed, perhapsfor years. In 1932 Washburn and Urey discovered the elec-trolytic separation of deuterium from hydrogen. Dihydrogengas generated by the electrolysis of water is depleted indeuterium. This fractionation explains the failure of Ureyand Murphy to find any significant enrichment in deute-rium in Brickwedde’s first sample. Brickwedde took specialprecautions before he undertook preparation of the en-riched samples. He took all of his equipment apart andcleaned it thoroughly to eliminate artifacts from impuri-ties. Most significantly, the electrolyte in the cell used togenerate the hydrogen to be liquefied was replaced by freshalkaline solution. Brickwedde literally threw the baby outwith the bath water. The dihydrogen produced from freshalkaline solution is depleted in deuterium. The Raleigh dis-tillation of this liquid hydrogen brought the deuterium con-


tent back to about natural abundance. As more and morewater is added to the electrolytic cell to replace that elec-trolyzed, the deuterium abundances rise to the natural abun-dance level.

THERMODYNAMIC PROPERTIES OF ISOTOPIC SUBSTANCES

Urey’s Nobel address was titled “Some ThermodynamicProperties of Hydrogen and Deuterium.” The first part cov-ered the discovery of deuterium. Two-thirds of the addressdealt with the differences in the thermodynamic propertiesof isotopes and the feasibility of isotope separation basedon these differences. By the time Urey initiated his work ondeuterium, calculation of the thermodynamic properties ofideal gases from spectroscopic data had been placed on afirm foundation. Such calculations are particularly simplewhen one compares the differences in behavior of isotopicsubstances. Under the assumption of the Born-Oppenheimerapproximation, the large enthalpy changes from the differ-ence in the minima of the potential energies of productsand reactants in a chemical reaction vanish for isotopicexchange reactions. Thus, Urey and Rittenberg calculatedthe differences in the degrees of dissociation of HCl(g)and DCl(g) and HI(g) and DI(g), respectively. They con-firmed their calculations with experiments on HI(g) andDI(g). Gould, Bleakney, and H. S. Taylor confirmed theUrey-Rittenberg calculations on the disproportionation ofHD into H2 and D2. The success of statistical mechanics topredict differences in the chemical properties of hydrogenand deuterium led Urey and Greiff to extend the methodto isotopomers of polyatomic molecules of carbon, nitro-gen, oxygen, and sulfur. For each of these elements, Ureyand Greiff found exchange reactions with enrichment fac-tors in the range from 1 to 4 percent at room temperature.

The predicted enrichment factors led Urey and Greiff to


suggest the chemical exchange method for the separationof isotopes of the light elements. The small elementary ef-fect was to be multiplied by countercurrent flow of two-phase systems. Each phase is to consist principally of onechemical species. When one phase is a liquid or liquid solu-tion and the other is vapor, the process is entirely analo-gous to distillation. In fact, distillation technology can bereadily adapted to chemical isotope separation. To replacethe boiler and condenser of a distillation tower, one re-quires chemical reactors that convert one chemical speciesto the other quantitatively. The exchange reaction must berapid and reversible. These principles led Urey and co-workersto develop the NH3(g)-NH+

4(sol’n.), HCN(g)-CN-(sol’n.), andSO2(g)-HSO-

3(sol’n.) reactions for the enrichment of 15N,13C, and 34S, respectively, during the 1930s. Each of thereactions developed by the Urey school involved acid-baseexchange reactions in aqueous solution. These are the fast-est chemical reactions. Reflux was achieved by cheap re-agents—acids and alkali. Compared with other isotope sepa-ration processes, centrifuges, and diffusion, the chemicalexchange process and the related liquid-vapor distillationhave large throughput per unit volume of separating equip-ment. Urey and T. I. Taylor also achieved a small enrich-ment of the lithium isotopes on zeolites, the forerunner ofthe ion exchange version of chemical isotope separation.

Most of the people who worked with Urey on isotopeseparation in the 1930s were postdoctoral fellows. This wasrather unusual for the time in American universities. Thesewere talented people interested in academic careers, forwhich there were few openings. In addition, there wereprofessionals, a chemical engineer with expertise in distilla-tion, and a recent Ph.D. in physics who built a Bleakney-type mass spectrometer for Urey’s program. Urey had nodifficulty getting support from foundations after he discov-


ered deuterium and received the Nobel Prize. In fact, hechose to share an award from the Carnegie Institution ofWashington with a member of the Physics Department, I. I.Rabi. Rabi never forgot Urey’s generosity and the impact ithad on his program on molecular beam research. Urey wasa good judge of talent; his investment in Rabi paid off hand-somely for science, the Carnegie Institution, and ColumbiaUniversity. Today, bureaucratic restrictions would make itimpossible for someone like Urey to give part of a grant toanother investigator, no matter how qualified or promising.

During the 1930s, Urey and his co-workers measured thevapor pressures of compounds enriched in D, 15N, and 18O.The values obtained for 18O were utilized in the partialenrichment of 18O by the distillation of water.

ISOTOPES AS TRACERS

Enriched stable isotopes of H, C, N, O, and S have foundwide application in agriculture, biology, chemistry, geology,and medicine. Urey used some of his enriched isotopes,particularly 18O, to carry out tracer studies. He and Cohnmeasured the acid and base catalyzed exchange betweenwater and acetaldehyde and acetone. They showed that ac-ids and alcohols do not exchange oxygen with water. Theyprovided the basis for Roberts and Urey to show unequivo-cally that it is the carbon-oxygen bond in the acid that isbroken in esterification reactions. Their result has been ofmajor importance in the elucidation of the mechanism ofthis important class of reactions. The use of 15N as a tracerin biochemistry was initiated by Rittenberg and Schoenheimerwith enriched samples supplied by Urey.

PALEOTEMPERATURES

When Urey moved from Columbia to the University ofChicago at the end of World War II, he decided not to


continue his interest in isotope separation or to undertakeany research with direct military application. His first prior-ity was to fill a prewar commitment to deliver the Liversidgelecture before the Chemical Society (London). For this pur-pose he decided to update and expand the earlier calcula-tions of Urey and Greiff on isotope exchange equilibriausing the advance method developed by Bigeleisen andGoeppert-Mayer at Columbia (SAM project) in 1943. Themethod afforded the possibility of calculating the tempera-ture coefficient of an isotope exchange equilibrium con-stant in addition to the logarithm of the constant with con-fidence. In the course of these calculations Urey noticedthat the fractionation factor for 18O/16O exchange betweenCO3

–2 and H2O(1) would decrease by 1.004 between O°and 25°C. Urey recognized the potential of utilizing thistemperature coefficient to measure paleotemperatures.

The method depended on the development of isotopicassay methods with a precision of better than 0.1 percent inthe 18O/16O ratio at the natural abundance level, which is0.2 percent. Nier and Thode had each developed the dualcollector method of measuring isotope ratios with a preci-sion of 0.1 percent of the ratio. There were additional re-quirements to be met if the method were to be useful.Isotope exchange equilibrium would have to be establishedin the precipitation of CaCO3 from H2O. The record wouldhave to be preserved over millions of years. It would benecessary to know the isotopic composition of the marinewater in equilibrium with the CaCO3. Urey assembled aresearch group that included graduate students, postdoctoralfellows, a paleogeologist, and an expert in electronics toattack these questions in a systematic way. They advancedthe precision of measurements of isotope ratios by almostan order of magnitude and routinely obtained a precisionof 0.02 percent in the 18O/16O ratio in CO2. In the applica-


tion of their method, an unknown sample was intercomparedwith a standard using a dual inlet system. The results wereexpressed in δ o/oo = [(Rsample/Rstandard) - 1] × 1,000. Thepaleotemperature scale was calibrated by the isotopic analy-sis of CaCO3 samples precipitated from water at known tem-peratures. The latter yielded a thermometric scale in termsof δ in good agreement with Urey’s calculation and subse-quent refined calculations by McCrea, a Ph.D. student. Thefinal proof of the paleotemperature-scale concept came withthe 1951 publication by Urey, Lowenstam, Epstein, andMcKinney. They analyzed the CaCO3 of a 100-million-year-old belemnite collected on the Isle of Skye by Cyril S. Smith.Samples of CaCO3 at various distances from the axis of thebelemnite core were analyzed for 18O/16O. They found thefossil had a life history of four winters and three summers.The winter temperatures were 15°C; the summer tempera-tures were 21°C. The winters grew progressively colder dur-ing the lifetime of the belemnite.

Urey and his group founded a new branch of geology,which has flourished under the leadership of his associatesand students and their students. For this achievement hereceived the Arthur L. Day Medal of the Geological Societyof America and the Goldschmidt Medal of the Geochemi-cal Society.

THE WAR YEARS, 1939-44: THE ATOMIC BOMB

Inasmuch as Harold Urey had studied with Bohr duringhis year in Copenhagen it was natural for him to attend theFifth Washington Conference on Theoretical Physics in Janu-ary 1939. It was at this conference that Bohr postulatedthat 235U was the fissionable isotope. The possible need forseparating the uranium isotopes was obvious. As the recog-nized world leader in isotope separation, Urey’s main po-tential contribution to fission research was clearly in that


field. He thus became one of the members of the dedicatedgroup of scientists, centered at Columbia University, whoinvestigated nuclear fission before government contracts wereavailable and who solicited and ultimately obtained govern-ment backing.

Two papers written by Urey in 1938, “The Separation ofIsotopes” (1939,1) and “Separation of Isotopes” (1939,5),throw light on the status of isotope separation at that timeand on Urey’s speculations about methods for separatingisotopes of the heavy elements. He proposed a countercur-rent flow centrifuge, designed to attain a number of stagesof separation in a single machine, thus reducing the num-ber of machines required in a cascade and the amount ofmaterial circulated between machines. Countercurrent flowin a machine was to be established by continuous distilla-tion of a liquid (uranium hexafluoride in the case of theuranium isotopes) from the bottom cap of the rotor andcondensation on the top cap. The liquid would then bethrown to the periphery and flow down the walls, counter-current to the vapor flow.

In a third paper, “Separation of Isotopes by ChemicalMeans” (1940,2), Urey concluded that separation of theuranium isotopes would lead to most interesting progressin the study of the fission process and discussed the cen-trifugal fractionation column (countercurrent flow centri-fuge) as affording the separation method most likely tosucceed. In early 1940 it was definitely established that 235Uwas the isotope fissionable by thermal neutrons. Urey, to-gether with a group of Columbia University faculty mem-bers, began work on uranium isotope separation in May1940, and a contract with President Roosevelt’s Committeefor Uranium for this work was executed in August. At ap-proximately the same time, Urey was appointed chairmanof an Advisory Committee on Nuclear Research to give tech-


nical advice to the Committee for Uranium. He coordi-nated experimental centrifuge studies at the University ofVirginia; gaseous diffusion separation research at Harvard;and thermal diffusion, chemical separation, and centrifu-gal fractionation at Columbia.

Urey undertook personal direction of research on chemi-cal separation of the uranium isotopes and on separationby the countercurrent centrifuge. The chemical separationinvolving uranium salts in immiscible solvents was not suc-cessful. The distilling centrifuge mentioned above was aban-doned in favor of an all-gas countercurrent centrifuge, thetheory for which was developed by Karl P. Cohen and thedesign was developed by Urey together with C. Skarstrom.Because some doubts had been raised by opponents of thecentrifuge project about the stability of countercurrent gas-eous flow, Cohen devised the theory and C. Skarstrom andUrey developed the design for a single-stage flow-throughcentrifuge. In early 1941 Westinghouse undertook to builda prototype of the flow-through design, a choice that hadfatal consequences for the centrifuge project.

The Advisory Committee on Nuclear Research was soonreorganized under Vannevar Bush’s National Defense Re-search Committee, and Urey and Dean George Pegram ofColumbia University became members of a new parent Com-mittee on Uranium. Urey had broad responsibilities for for-mulating the whole research program.

In view of some uncertainty in 1940 with respect to thefeasibility of a divergent chain reaction using natural ura-nium with graphite moderator, Urey became interested inthe use of heavy water as an alternative moderator becauseof its greater efficiency and its practically zero neutron ab-sorption cross-section. Urey proposed using catalytic exchangebetween hydrogen and water to produce heavy water in


quantity. He invited professor H. S. Taylor of Princeton tostudy this process.

Centrifuge work was undertaken in early 1941 byWestinghouse in Pittsburgh and also was continuing at theUniversity of Virginia. Urey turned his attention to the gas-eous diffusion process. He reported in November 1940 aninitial appraisal of separation by diffusion through porousbarriers. K. P. Cohen measured the first actual separationby barriers using CO2/H2 mixtures. Estimates of plant sizebased on these observations showed that a diffusion separa-tion plant would involve as large an undertaking as thecentrifuge plant.

The last half of 1941 found the uranium program in astage of constant ferment. Plutonium had been shown tobe fissionable. The English gaseous diffusion process seemedlikely to succeed, and the Columbia diffusion system wasnot far enough along to evaluate properly. Work in Britainindicated metallic uranium, and heavy water provided thebest route to a chain reaction. The British were convincedthat weapons could be made from reasonably small quanti-ties of 235U. The Uranium Committee was reorganized. Anew Office of Scientific Research and Development was cre-ated in the Executive Office of the President as the centerfor the application of science to national defense, and Ureywas a member of its Section on Uranium. He was givenresponsibility for uranium isotope separation by exchangemethods and for heavy water production. V. Bush and J. B.Conant had overall responsibility for the uranium program.The chain reaction program was reoriented to plutoniumproduction and weapons production. An electromagneticseparation project had been initiated.

By the end of 1941 and early 1942 the program movedfrom the research to the engineering and construction phases.The attempt to arouse the government to the military po-


tential of uranium fission had finally succeeded. The chainreaction group at Columbia, headed by Fermi and Szilard,was moved to the University of Chicago. The scope of Urey’sdirect responsibilities in 1942 included the English diffu-sion separation method, the American diffusion method,and the centrifugation method. A decision had been madeto transfer all uranium work to the United States, and Ureytook special pains to see that the British diffusion ideaswere seriously considered.

In May 1942 the Section on Uranium’s Executive Com-mittee, of which Urey was a member, was asked by J. B.Conant to recommend a program to build atomic weapons.Their proposal to Conant showed strong input from Ureyin that it placed great emphasis on centrifuges and heavywater production. This program included construction of acentrifuge plant, a gaseous diffusion pilot and productionplant, an electromagnetic plant, pile production of element94, and a plant for heavy water production. It was estimatedthat the proposed plans would result in the production of afew atomic bombs by July 1944.

In the summer of 1942 the reported experimental resultson flow-through centrifuges were disappointing, showingonly 36 percent of theoretical efficiency. Urey’s protesta-tions that countercurrent centrifuges would be easier tobuild and were more efficient were to no avail. Centrifugework remained at a low level. It is an irony of history thatsubsequent experiments in 1943 and 1944 proved that coun-tercurrent machines could operate close to theoretical effi-ciency. At least six nations have at the present time oper-ated countercurrent centrifuges with UF6, and it is theuranium isotope separation method of choice for five ofthem.

In November and December of 1942 there was a commit-ment to a full-scale diffusion plant, a smaller electromag-


netic plant convertible later to full size, and heavy waterplants.

The research organization at Columbia University underHarold Urey’s direct supervision had been growing rapidly.In 1942 and 1943 Urey attracted many eminent scientistsfrom academia and industr y to assist in the development ofcomponents of the diffusion plant and in his other activi-ties. By the end of 1943 Urey had more than 700 peopleworking on gaseous diffusion alone and several hundredmore, including those at other universities and industriallaboratories, working on various other researches. He hadlittle taste for administration, and the burden weighed heavilyon him.

This effort produced some notable successes. A new pro-cess was devised for producing heavy water, based on dual-temperature exchange between hydrogen sulfide and wa-ter. A successful method for separating the boron isotopeswas developed for production of the crystalline 10B neededat Los Alamos. Low-leakage seals for rotating equipmentand mass spectrometers for process analysis, and leak de-tectors, needed for both laboratory research and plant con-struction, were devised and produced. Progress was madeon fundamental theory of separation by diffusion barriers.

However, the barrier remained recalcitrant. Copper bar-riers were abandoned, and efforts were concentrated onnickel barriers. Both electrodeposited (Norris-Adler) andcompressed powder barriers were tried. As 1943 wore on, itwas realized that, despite heroic efforts, barriers with theproperties, uniformity and ruggedness necessary for manu-facture were not available. Nevertheless, a pilot plant formanufacture of the electrodeposited barrier was being com-pleted.

Difficulties were also becoming apparent in the otherproduction projects. The electromagnetic separators that


had been installed in Oak Ridge, Tennessee, were experi-encing severe operational problems. The laboratory in Chi-cago was openly critical of time schedules and of the graph-ite pile design that had been developed by the DupontCompany.

Urey saw his hopes for a contribution from the uraniumprogram to the imminent 1944 war crisis fade, even as hisfears of a German atom bomb remained lively. He renewedhis efforts to realize a homogeneous heavy water uraniumslurry reactor, proposed by Halban, for plutonium produc-tion. This led to the research piles in Chicago and later inthe 1950s to the Savannah River plutonium production re-actors. Urey championed P. Abelson’s liquid thermal diffu-sion process, which seemed a last hope to achieve timelyweapons production. A plant was hastily authorized in OakRidge in the second half of 1944 and was used to enrichthe feed to the electromagnetic plant.

In the autumn of 1943 a new type of diffusion barrier,combining features of both the electrodeposited and com-pressed powder barriers that had been previously devel-oped, was proposed by the Kellex Corporation. In the springof 1944 a plant began producing acceptable barrier mate-rial of the previously developed electrodeposited type, whoseproduction had been urged by Urey. Ten thousand workershad been building a huge diffusion plant at Oak Ridge.Early in 1944 the Army (General L. R. Groves command-ing) made the decision to rely on the barrier developed atKellex. Fortunately, both types of barrier eventually provedsatisfactory. The first production from the gaseous diffu-sion plant occurred in March 1945. The plant operatedwith unprecedented reliability and economy during the post-war period, superseding all other methods, but most of the235U for the Hiroshima bomb was produced by the electro-magnetic separation plant.


Early in 1944 when the decision was made to rely on thenew barrier being developed by Kellex, it was clear to Ureythat the diffusion plant would have little relevance to thewar effort. He relinquished barrier development to his as-sociate directors. Urey remained nominal head of the Co-lumbia laboratories until 1945, but his heart was not in it.From that time forward his energies were directed to thecontrol of atomic energy, not its application.

COSMOCHEMISTRY

Urey moved from Columbia to Chicago in 1945. Shortlythereafter he read a book by Ralph Baldwin, The Face of theMoon, which started him on a love affair with that object,which continued for the rest of his career. Colleagues atChicago, or any available listeners, would be treated to mono-logues, sprinkled with the names of craters and other tech-nical terms, which were impressive though bewildering. Ureycame to regard study of the moon as a key to understand-ing the origin of the solar system. This led to a sustained,audacious attack on the broader problem.

His 1952 book, The Planets, is generally agreed to havebegun the modern science of the solar system; it broughtthe term “cosmochemistry,” as distinguished from geochem-istry, into the language. The work systematized the state ofour knowledge at that time and set forth a research agendaemphasizing physicochemical and chronological study ofmeteorites, the oldest and least altered materials in ourpossession.

Two papers out of many in the following years were espe-cially influential. Craig and Urey (1953,1) reclassified themeteorites using chemical criteria and set the stage for de-tailed comparison between meteorite (chrondite) chemicalabundances and those of nonvolatile elements in the sunand other stars. Suess and Urey (1956,2) used meteoritic


and solar abundances to make an improved table of abun-dances of the elements, showing clearly the influence ofnuclear shell closure and other specific nuclear effects onelemental and isotopic abundances. This paper was the ba-sis for the first successful account of the origin of the chemicalelements in stars by Burbidge, Burbidge, Fowler, and Hoyle(1957). The intimate interplay between chemical and astro-physical problems became widely understood for the firsttime.

It is sobering to realize that when Urey wrote The Planetseven so basic a fact as the age of the earth was not yetsettled. He began to look for experimental areas beyondthe 18O/16O system where his mass spectrometric skills couldbe applied. A young graduate student named JerryWasserburg turned up at Chicago, and Urey put him towork on the 40K/40Ar isotopic dating system. His thesis,which involved collaboration with R. J. Hayden of the ArgonneNational Laboratory and Professor Mark Inghram, was afirst step on the path by which Wasserburg made a numberof fundamental contributions to geochronology in subse-quent decades.

Urey took great interest in the existence of diamonds intwo classes of meteorites: stony objects called ureilites (notnamed for him) and big metallic meteorites like the onethat made Meteor Crater in Arizona. He hoped that thediamonds were formed in thermodynamic equilibrium athigh pressures. We know now that in the iron objects theywere formed by shock; the situation in the ureilites is notso clear.

It was a natural step for a chemist thinking about theorigin of the planets to think about the origin of life onthis particular one and perhaps on Mars or elsewhere. Startingfrom the abundance of hydrogen in the sun and other stars,and the abundance of methane in the outer planets, Urey


concluded that it was likely that the earth’s atmosphere wasoriginally reducing, rich in CH4 and NH3 rather than CO2and N2. He suggested that thermodynamics favored the for-mation of organic compounds in such an atmosphere.

Not long after this a graduate student named StanleyMiller presented himself to Urey and proposed to do anexperimental thesis testing this hypothesis in the labora-tory. Urey told him it was too difficult for a thesis problem,but Miller won a grudging permission to try. Within a monthhe was exhibiting organic muck in a flask containing meth-ane, ammonia, and water, excited by an electric dischargeas a model for lightning discharges in such an atmosphere.Miller showed that the solution products contained aminoacids and other possible precursor compounds for life.

Some of us were present at a crowded seminar in whichMiller presented his results, with Urey in the front row. Bythe end of the presentation it was obvious to all that thiswas an important milestone. In the question period EnricoFermi turned to Urey and said, “I understand that you andMiller have demonstrated that this is one path by which lifemight have originated. Harold, do you think it was the way?”Urey replied, “Let me put it this way, Enrico. If God didn’tdo it this way, he overlooked a good bet!” Today the as-sumed early reducing atmosphere is no longer widely ac-cepted, but the impetus given by Urey still remains.

THE LA JOLLA YEARS

In 1958 Urey passed a milestone—his sixty-fifth birthday.When it became clear that he would then become emeritusat the University of Chicago, his friends at the newly form-ing University of California, San Diego, led by Roger Revelle,offered him an appointment there, and he accepted. Thatwas the year after the Soviet launch of Sputnik I, and na-tional attention was focused on space. The National Aero-


nautics and Space Administration also was new, and thefirst U.S. satellites were reaching orbit after some embar-rassing failures.

At UCSD Urey joined a small number of younger facultymembers who were planning a major university with a strongscience and engineering side. He immediately started up avigorous research program, involving both carbon and oxy-gen isotopic measurements (for paleotemperatures and otherpurposes) and comparable data for heavier solid and gas-eous elements for dating. At the same time, his presenceon campus gave a mark of quality to the place that othernew foundations could not match. While professing himselfunsuitable for any administrative functions, Urey was flyingto Washington frequently to press advice on the new spaceagency. According to Robert Jastrow, it was Urey who per-suaded NASA to make unmanned missions to the moon anearly focus of its space efforts.

In 1960 UCSD formed its Department of Chemistry, withUrey as one of its founding members. Others were old friendsand disciples—Joe Mayer, Jim Arnold, Hans Suess, and StanleyMiller. Urey was particularly emphatic about the importanceof biochemistry, which became a major component of thedeveloping department. In the following years he influencedthe department and university mainly by example.

Urey was very active at the time of Apollo 11, when thefirst lunar samples were returned and the first data wereappearing. Though he (unfortunately) almost never talkedabout the past, he told his colleagues one story that time.He told us that it was only in 1910, when he was seventeenyears old, that he saw his first automobile in rural Montana.Less than sixty years later his friends showed him the firstrock returned from the moon, an achievement in which hehad played a significant role.

His powers of concentration, even into his eighties, were


remarkable. He could think intensively about one problemfor long periods; his well-known absentmindedness was theinverse of his sharp focus on one important problem at atime. He loved science.

One scene may give the flavor of the man at the end ofhis career. On any given morning he might burst into theoffice of a colleague eager to talk. Seeing the colleagueperhaps discussing current research with students, he wouldapologize and begin to back out. Of course, he was invitedin. He would then rush to the blackboard and begin “I’vefinally figured out. . . .” He would soon be pouring outwords faster than even close associates could assimilate them.“Does that seem right?” he would say at the end. Maybe onequestion or comment would emerge. He’d thank the groupwarmly, again apologize, and rush out. The effect of thisdisplay on young graduate students was remarkable.

Urey’s last two scientific papers were written and pub-lished in 1977, when he was eighty-four years old. Yearsearlier the largest research building on campus, housingchemists and engineers, had been christened the Haroldand Frieda Urey Hall, to recognize the role they both playedin the founding and early development of UCSD.

UREY’S PERSONAL LIFE AND HIS POLITICAL AND

EDUCATIONAL ACTIVITIES

Thus far we have been concerned with the scientificachievements of Harold Urey. He is also well rememberedby all who knew him as a person intensely interested in thewell-being of his fellow man. This concern was displayednot only for his students, research associates, and facultycolleagues but also with respect to social and political prob-lems of national and international importance. He had agreat interest in such problems, some of them closely re-lated to the wartime work with which he had been involved.


He devoted the same concentrated effort and careful thoughtto their possible solutions as he did to the solving of theproblems of his scientific researches. Having concluded thatcertain actions were required, he then, with the same vigorand determination that were characteristic of his scientificwork, would bend every effort toward furthering these ac-tions.

While at Columbia University he had been chairman ofthe University Federation for Democracy and IntellectualFreedom and a champion of loyalist Spain. As early as 1932he espoused Clarence Streit’s Atlantic Union plan for aworld governmental federation. He became greatly disturbedby the rise of Hitler and the progress of Nazism. He wasactive in securing posts for refugee scientists and in extend-ing his hospitality to them when they arrived in this coun-try. In her book Atoms in the Family, Laura Fermi recountshow Harold and his wife Frieda helped her and her hus-band Enrico become their neighbors in Leonia, New Jersey,when the Fermis arrived at Columbia University from Italy.

As World War II ended, Urey, then at the University ofChicago, became concerned and worried about the poten-tial of atomic bombs, in whose creation he had played suchan important role. His interest in world government, be-gun at Columbia University, returned with renewed vigor.He worked diligently on the public speaker’s platform and,through his writings presented in the press, toward the cre-ation of a world free of the dangers and dread of war.

During this period of lecturing and writing on the prob-lems created by nuclear energy developments, Urey activelyopposed congressional passage of the May-Johnson bill, whichhe feared would permit military control of peacetime ac-tivities in the field of nuclear energy. He strongly supportedthe eventual McMahon bill in its final form and was a leaderin the fight for its passage. His doubts concerning the jus-


tice of the executions of Ethel and Julius Rosenberg foratomic energy secrecy violations received national attention.His views on this matter were not ones that were popularwith large sections of the American public. He was calledbefore the House Un-American Activities Committee. Hewrote, “I doubted seriously if justice had been done. I wasonly interested in one question. Had they indeed violatedthe laws of the United States and had justice been done? Itis my firm conviction that justice was not done in that case.”

Harold Urey was an educator, in the undergraduate andgraduate classroom, in the research laboratory, and on thepublic platform. At the end of World War II, he returned toteaching at a time when many, including himself, felt thatthis country had, in the course of intensive war research,temporarily abandoned both basic research and the train-ing of a new generation of scientists. At this time, whenmany were worried about how to keep the “secret” of theatomic bomb and how to prevent dominance by the SovietUnion, he wrote, “The real problem that faces this countryis a long-term one. It is a problem of the proper educationand inspiration of our youth.” He approached with greatzest the teaching not only of graduate students but also offirst-year undergraduate chemistry courses. His interest inthe “inspiration of our youth” even extended to public gradeschools. His wife Frieda wrote, “He enjoyed nothing so muchas taking his moon-globe to the fifth grade class in the LaJolla schools and telling the students about the moon andthe planets.”

Harold was fond of and proud of his family. While atJohns Hopkins University, he visited his mother, then livingin Seattle. While on that visit he renewed his acquaintancewith a friend from his University of Montana days, and sheintroduced him to her younger sister Frieda Daum, whowas working as a bacteriologist. As Roger Revelle of La Jolla


described it, “Harold Urey was never thought of as an out-door man but he spent the next two weeks hiking in theCascade Mountains with Frieda. Within a year they weremarried and their careers as mountaineers were ended. Af-ter that Harold’s outdoor activity was confined to his gar-den.” Frieda and Harold had three daughters (Elizabeth,Frieda, and Mary Alice) and one son (John). At the timeHarold was notified of the award of the Nobel Prize, Friedawas expecting their third child. In order to be with Friedahe did not attend the December 10 ceremonies in Stockholm.Mary Alice was born on December 2, and Frieda and Haroldsailed for Stockholm the following February and attendeda special award ceremony.

The friendliness and hospitality of Harold and Friedaand their family brought people together socially in a waythat created a most pleasant academic atmosphere and addedgreatly to the enjoyment of life on the part of the familiesof Harold’s fellow faculty members and of the research as-sociates and students in the universities of which he was amember.

Harold was greatly concerned with the welfare of his sci-entific colleagues, students, and postdoctoral research asso-ciates. He was always interested in his students’ develop-ment of their own independent scientific careers. He wasconcerned that they be established in suitable posts uponcompletion of their researches in his laboratory and wasactive in locating suitable academic and other positions forthem. He was diligent in seeing that they received appro-priate credit for their work under his supervision. The firstpaper on the establishment of the Urey paleotemperaturescale was published under the sole authorship of his stu-dent John McCrea. Likewise at Urey’s insistence, the soleauthor of the first article on the Urey-Miller theory and


experiment on the origin of terrestrial life was his studentStanley Miller.

Abolition of the boundaries between scientific disciplineswas a basic tenet of Urey’s philosophy. His own academiccareer, described above, was exemplary in this respect. Con-cerning his stay at Bohr’s Institute for Theoretical Physicshe said, “Bohr didn’t know I was a chemist. He thought Iwas a physicist.” He claimed he had learned most of hisphysics in Copenhagen restaurants while dining with Pro-fessor H. A. Kramers. In 1933 Harold founded the interdis-ciplinary Journal of Chemical Physics, which provided an ap-propriate medium for publication of the already-large bodyof work that bridged the traditional fields of chemistry andphysics. He became the first editor of that journal, a posi-tion he held until 1940, by which time it had become aleading scientific journal.

Urey may be considered to have established at least fourfields of scientific research: stable isotope chemistry, includingisotope geochemistry, geochronology, and isotope separa-tion; paleotemperature measurement; cosmochemistry; andthe origin of terrestrial life. The scope of his interests andinfluence are reflected in the thirty-two chapters of themonograph Isotopic and Cosmic Chemistry contributed by formerstudents, postdoctoral associates, and colleagues on the oc-casion of his seventieth birthday. Karl Cohen, in an obitu-ary in the Bulletin of the Atomic Scientists, said, “Urey’s pio-neering work underlies every method of isotope separationsuccessfully employed on a large scale, for every elementfrom hydrogen to uranium.” Craig, Miller, and Wasserburg,in their introduction to Isotopic and Cosmic Chemistry, wrote,“The measurement of the paleotemperatures of the ancientoceans stands as one of the great developments of the earthsciences; a truly remarkable scientific and intellectual achieve-ment.” Cohen, Runcorn, Suess, and Thode in the Biographi-


cal Memoirs of the Royal Society of London, speaking of Haroldas “the founder of the field of cosmochemistry” wrote, “Urey,undoubtedly, was the first who rigorously defined this fieldby its problems and by asking precise questions.” His ideasconcerning the primordial atmosphere and the beginningof life on earth opened up a completely new approach tothe study of the origin of life on this planet.

Urey’s vigorous and concentrated pursuit of these re-searches and his enthusiastic interactions with those aroundhim concerning his latest ideas continued to the end of hislife. After his retirement at age sixty-five from the Univer-sity of Chicago and his arrival at the University of Califor-nia, his work continued with unabated intensity, and hepublished 105 scientific papers, 47 of them concerned withhis study of the moon, in the remaining twenty-three yearsof his life. Some ten years after his retirement from Chi-cago he was asked by Professor James Arnold in La Jolla,“Harold, why do you put in so many hours at work?” Ureyreplied, “Well, you know I’m not on tenure anymore.”

WE ACKNOWLEDGE THE ASSISTANCE of Elizabeth Urey Baranger, KarlP. Cohen, and Stanley L. Miller in the preparation of this memoir.


HAROLD CLAYTON UREY

Born: Walkerton, Indiana / April 29, 1893Married: June 12, 1926 to Frieda DaumChildren: Gertrude Elizabeth Baranger

Frieda Rebecca BrownMary Alice LoreyJohn Clayton Urey

Hobbies: Gardening and raising orchids (cattleya, cymbidium,and others)

EDUCATION

University of Montana, Missoula, 1914-17, B.S. in biology with aminor in chemistry

University of California, Berkeley, 1921-23, Ph.D. in chemistry witha minor in physics

American-Scandinavian Foundation Fellow, Niels Bohr Institutefor Theoretical Physics, Copenhagen, 1923-24

PROFESSIONAL EMPLOYMENT

1911-14 Teacher in rural schools in Indiana, 1911-12; Montana,1912-14

1918-19 Barrett Chemical Co., Baltimore, research chemist1919-21 University of Montana, instructor in chemistry1924-29 Johns Hopkins University, associate in chemistry1929-36 Columbia University, associate professor of chemistry,

1929-34; Ernest Kempton Adams Fellow, 1933-36;professor of chemistry, 1934-45; executive officer,Department of Chemistry, 1939-42; director of warresearch, SAM Laboratories, 1940-45

1933-40 Journal of Chemical Physics, editor1945-58 University of Chicago, Institute for Nuclear Studies:

Distinguished Service Professor of Chemistry, 1945-52;Martin A. Ryerson Distinguished Service Professor ofChemistry, 1952-58

1956-57 Oxford University, George Eastman Visiting Professor1958-70 University of California, San Diego, professor of

chemistry-at-large


H O N O R S , P R I Z E S , A N D AWA R D S

1934 Nobel Prize, ChemistryWillard Gibbs Medal, American Chemical Society

1935 Silver Medal, Research Institute of America1940 Davy Medal, Royal Society, London1943 Franklin Medal, Franklin Institute1945 Manhattan Project Certificate of Award for Service, U.S.

War Department1946 Medal of Merit, President Harry S. Truman1950 Distinguished Service Award, Phi Beta Kappa

Centennial Award, Northwestern University1957 Jesuit Centennial Citation, Chicago1960 Silver Medal, Research Institute of America

Cordoza Award, Tau Epsilon Rho Law Fraternity1961 Alexander Hamilton Award, Columbia University1962 J. Lawrence Smith Medal, National Academy of Sciences1963 Remsen Memorial Award, American Chemical Society,

Baltimore Section1964 University of Paris Medal

National Medal of Science1966 Gold Medal, Royal Astronomy Society, London

American Academy of Achievement Award, Golden PlateAward

1967 Man of Distinction Award, Women’s Guild of TempleEmanu-El, San Diego

1969 Chemical Pioneer Award, American Institute of ChemistsArthur L. Day Medal, Geological Society of AmericaLeonard Medal, Meteoritic Society

1970 Linus Pauling Award, Oregon State University1971 400th Anniversary of Johann Kepler Medal and Citation,

American Academy of Arts and Sciences1972 Gold Medal Award, American Institute of Chemists1973 Honorary Council and Medal, Higher Council of Scientific

Research, BarcelonaSilver Medal, 50th Anniversary of International Fair ofBarcelonaKnights of Malta AwardPriestley Medal, American Chemical Society


NASA Medal for Exceptional Scientific Achievement1974 Headliner Award, San Diego Press Club

Medallion, Honorary Member of Indiana Academy,IndianapolisDedication of the Harold C. Urey Laboratory for IsotopicPaleotemperature Research, University of Miami, CoralGables, Florida.

1975 V. M. Goldschmidt Medal, Geochemical Society1976 NASA Group Achievement Award, U.S. Members of Joint

Editorial Board for Foundations of Space Biology andMedicine, for joint US/USSR treatise

1978 Honorary member UCSD chapter of Phi Beta Kappa

HONORARY DEGREES

1935 Princeton University, D.Sc.University of Montana, D.Sc.

1939 Rutgers University, D.Sc.1946 Columbia University, D.Sc.

Oxford University, D.Sc.1948 Washington & Lee University, D.Sc.1951 Yale University, D.Sc.

University of AthensMcMaster University, D.Sc.

1953 Indiana University, D.Sc.1955 University of California, LL.D.1957 University of Birmingham, D.Sc.

University of Durham, D.Sc.1958 Wayne State University, LL.D.1959 Hebrew Union College, Jewish Institute of Religion, D.H.L.1960 University of Saskatchewan, D.Sc.1962 Israel Institute of Technology, D.Sc.1963 Gustavus Adolphus College, D.Sc.

University of Pittsburgh, D.Sc.University of Chicago, D.Sc.

1965 University of Notre Dame, LL.D.1966 University of Manchester, D.Sc.1967 University of Michigan, D.Sc.1969 Franklin and Marshall College, D.Sc.1970 McGill University, D.Sc.


PROFESSIONAL ASSOCIATIONS

Academia Scientiarum Olisiponensis, Lisbon (Lisbon Academy ofSciences)

Academie Royale des Sciences, des Lettres et des Beaux Arts deBelgique (Honorary)

American Academy of Arts and SciencesAmerican Association for the Advancement of ScienceAmerican Association of University ProfessorsAmerican Astronomical SocietyAmerican Astronautical Society (fellow)American Chemical SocietyAmerican Geophysical Union (honorary fellow)American Institute of Chemists (honorary)American Philosophical SocietyAmerican Physical SocietyAssociacion Venezolana para el Avance de la Ciencia (honorary)Chemical Society, London (honorary fellow)Federation of American Scientists (life member)Franklin Institute (honorary)French Chemical Society (honorary)German Society of Aeronautics and Astronautics (honorary)Geological Society of AmericaIllinois State Academy of ScienceInternational Association of Geochimica and CosmochimicaInternational Astronautical AcademyInternational Platform AssociationMellon Institute (honorary)Meteoritical Society (fellow)National Academy of SciencesNational Institute of Sciences of India (honorary)Phi Sigma Biological Society (honorary)Royal Astronomical Society, London (associate)Royal Institution, London (honorary)Royal Irish Academy (honorary)Royal Society, London (foreign member)Royal Society of Arts and Sciences, GöteborgRoyal Swedish Academy (honorary)Smithsonian National AssociationSociété Royale des Science de Liège (foreign member)


Weizmann Institute of Science (honorary fellow)World Academy of Arts and Sciences, American Division

(corresponding member)

CLUBS

Chemists’ Club, New York (honorary)CosmosQuadrangle and Tavery (Chicago)


S E L E C T E D B I B L I O G R A P H Y

1923

The heat capacities and entropies of diatomic and polyatomic gases.J. Am. Chem. Soc. 45:1445-55.

1924

The distribution of electrons in the various orbits of the hydrogenatom. Astrophys. J. 59:1-10.

On the effect of perturbing electric fields on the Zeeman effect ofthe hydrogen spectrum. Klg. Danske Videnskabernes Selskab, Math.-fys. Medd. 6:11-19.

1925

The structure of the hydrogen molecule ion. Proc. Natl. Acad. Sci.U.S.A. 11:618-21.

1926

With Y. Sugiura. The quantum theory explanation of the anomaliesin the 6th and 7th periods of the periodic table. Klg. DanskeVidenskabernes Selskab, Math.-fys. Medd. 7:3-18.

With F. R. Bichowsky. A possible explanation of the relativity dou-blets and anomalous Zeeman effects by means of a magneticelectron. Proc. Natl. Acad. Sci. U.S.A. 12:80-85.

1927

With A. E. Ruark. Impulse moment of the light quantum. Proc. Natl.Acad. Sci. U.S.A. 13:763-71.

1928

With F. O. Rice and R. N. Washburne. The mechanism of homoge-neous gas reactions. I. The effect of black-body radiation on amolecular beam of nitrogen pentoxide. J. Am. Chem. Soc. 50:2402-12.

1929

With L. H. Dawsey and F. O. Rice. The absorption spectrum and


decomposition of hydrogen peroxide by light. J. Am. Chem. Soc.51:1371-83.

With L. H. Dawsey and F. O. Rice. The mechanism of homogeneousgas reactions. II. The absorption spectrum of nitrogen pentoxideand its method of decomposition. J. Am. Chem. Soc. 51:3190-94.

With G. I. Lavin. Some reactions of atomic hydrogen. J. Am. Chem.Soc. 51:3286-90.

1930

With H. Johnston. Regularities in radioactive nuclei. Phys. Rev. 35:869-70.

With A. E. Ruark. Atoms, Molecules and Quanta. New York: McGraw-Hill.

1931

With C. A. Bradley, Jr. Raman spectrum of silicochloroform. Phys.Rev. 37:843.

The masses of O17. Phys. Rev. 37:923-29.With G. M. Murphy. The relative abundance of N14 and N15. Phys.

Rev. 38:575-76.The alternating intensities of sodium bands. Phys. Rev. 38:1074-75.With C. A. Bradley, Jr. The vibrations of pentatomic tetrahedral

molecules. Phys. Rev. 38:1969-78.With H. Johnston. The absorption spectrum of chlorine dioxide.

Phys. Rev. 38:2131-52.The natural system of atomic nuclei. J. Am. Chem. Soc. 53:2872-80.

1932

Nuclear structure. Nature 130:403.With F. G. Brickwedde and G. M. Murphy. A hydrogen isotope of

mass 2. Phys. Rev. 39:164-65.With F. G. Brickwedde and G. M. Murphy. A hydrogen isotope of

mass 2 and its concentration. Phys. Rev. 40:1-15.With F. G. Brickwedde and G. M. Murphy. Relative abundance of

H1 and H2 in natural hydrogen. Phys. Rev. 40:464-65.With C. A. Bradley, Jr. The relative abundance of hydrogen isotopes

in natural hydrogen. Phys. Rev. 40:889-90.With E. W. Washburn. Concentration of the H2 isotope of hydrogen


by the fractional electrolysis of water. Proc. Natl. Acad. Sci. U.S.A.18:496-98.

With G. M. Murphy. The relative abundance of the nitrogen andoxygen isotopes. Phys. Rev. 41:141-48.

1933

Editorial. J. Chem. Phys. 1:1-2.With D. Rittenberg. Some thermodynamic properties of the H1H2

and H2H2 molecules and compounds containing the H2 atom. J.Chem. Phys. 1:137-43.

With J. Joffe. The spin of the sodium nucleus. Phys. Rev. 43:761.Separation and properties of the isotopes of hydrogen. Science 78:566-

71.With R. H. Crist and G. M. Murphy. Isotopic analysis of water. J.

Am. Chem. Soc. 55:5060-61.

1934

With D. Rittenberg and W. Bleakney. The equilibrium between thethree hydrogens. J. Chem. Phys. 2:48-49.

With R. H. Crist and G. M. Murphy. The use of the interferometerin the isotopic analysis of water. J. Chem. Phys. 2:112-15.

With D. Price. The synthesis of tetradeuteromethane. J. Chem. Phys.2:300.

With V. K. LaMer and W. C. Eichelberger. Freezing points of mix-tures of H2O and H2

2O. J. Am. Chem. Soc. 56:248-49.With F. G. Brickwedde, R. B. Scott, and M. H. Wahl. The vapor

pressure of deuterium. Phys. Rev. 45:566.With M. H. Wahl. A cascade electrolytic process for separating the

hydrogen isotopes. Phys. Rev. 45:566.Significance of the hydrogen isotopes. Ind. Eng. Chem. 26:803-6.Deuterium and its compounds in relation to biology. Cold Spring

Harbor Symp. 2:47-56.With R. B. Scott, F. G. Brickwedde, and M. H. Wahl. The vapor

pressure and derived thermal properties of hydrogen and deute-rium. J. Chem. Phys. 2:454-64.

With D. Rittenberg. Thermal decomposition of deuterium iodide. J.Am. Chem. Soc. 56:1885-89.

With S. H. Manian and W. Bleakney. The relative abundance of the


oxygen isotopes O16:O18 in stone meteorites. J. Am. Chem. Soc.56:2601-9.

1935

With L. A. Weber and M. H. Wahl. Fractionation of the oxygenisotopes in an exchange reaction. J. Chem. Phys. 3:129.

With M. H. Wahl. Vapor pressures of the isotopic forms of water. J.Chem. Phys. 3:411-14.

Some thermodynamic properties of hydrogen and deuterium. In LePrix Nobel en 1934, pp. 1-10. Stockholm: Kungl. Baklryckenet. Alsopublished in Angew. Chem. 48:315-20.

With L. J. Greiff. Isotopic exchange equilibria. J. Am. Chem. Soc.57:321-27.

With G. K. Teal. The hydrogen isotope of atomic weight two. Rev.Mod. Phys. 7:34-94.

1936

With A. H. W. Aten, Jr. On the chemical differences between nitro-gen isotopes. Phys. Rev. 50:575.

With G. E. MacWood. Raman spectra of the deuteriomethanes. J.Chem. Phys. 4:402-6.

With A. H. W. Aten, Jr., and A. S. Keston. A concentration of thecarbon isotope. J. Chem. Phys. 4:622-23.

With G. B. Pegram and J. R. Huffman. The concentration of theoxygen isotopes. J. Chem. Phys. 4:623.

1937

With T. I. Taylor. The electrolytic and chemical-exchange methodsfor the separation of the lithium isotopes. J. Chem. Phys. 5:597-98.

With J. R. Huffman, H. G. Thode, and M. Fox. Concentration ofN15 by chemical methods. J. Chem. Phys. 5:856-68.

1938

Chemistry and the future. Science 88:133-39.With M. Cohn. Oxygen exchange reactions of organic compounds

and water. J. Am. Chem. Soc. 60:679-87.With I. Roberts. The exchange of oxygen between benzil and water

and the benzilic acid rearrangement. J. Am. Chem. Soc. 60:880-82.


With I. Roberts. Esterification of benzoic acid with methyl alcoholby use of isotopic oxygen. J. Am. Chem. Soc. 60:2391-93.

With H. G. Thode and J. E. Gorham. The concentration of N15 andS34. J. Chem. Phys. 6:296.

With T. I. Taylor. Fractionation of the lithium and potassium iso-topes by chemical exchange with zeolites. J. Chem. Phys. 6:429-38.

1939

The separation of isotopes. In Recent Advances in Surface Chemistryand Chemical Physics, pp. 73-87. Washington, D.C.: American Asso-ciation for the Advancement of Science.

With K. Cohen. Van der Waals’ forces and the vapor pressures ofortho- and parahydrogen and ortho- and paradeuterium. J. Chem.Phys. 7:157-63.

With I. Roberts. Kinetics of the exchange of oxygen between ben-zoic acid and water. J. Am. Chem. Soc. 61:2580.

With I. Roberts. Mechanisms of acid catalyzed ester hydrolysis, es-terification, and oxygen exchange of carboxylic acids. J. Am. Chem.Soc. 61:2584.

Separation of isotopes. In Reports on Progress in Physics, vol. 6, pp. 48-77. London: The Physical Society.

1940

With C. A. Hutchison, Jr., and D. W. Stewart. The concentration ofC13. J. Chem. Phys. 8:532-37.

Separation of isotopes by chemical means. J. Wash. Acad. Sci. 30:277-94.

With G. A. Mills. The kinetics of isotopic exchange between carbondioxide, bicarbonate ion, carbonate ion and water. J. Am. Chem.Soc. 62:1019-26.

1942

With E. Leifer. Kinetics of gaseous reactions by means of the massspectrometer. The thermal decomposition of dimethyl ether andacetaldehyde. J. Am. Chem. Soc. 64:994-1001.

With I. Kirshenbaum. The differences in the vapor pressures, heatsof vaporization, and triple points of nitrogen (14) and nitrogen(15) and of ammonia and trideuteroammonia. I. J. Chem. Phys.10:706-17.


1943

With A. F. Reid. The use of the exchange between CO2, H2CO3,HCO3 ion and H2O for isotopic concentration. J. Chem. Phys.11:403-12.

1945

With J. D. Brandner. Kinetics of the isotopic exchange reactionbetween carbon monoxide and carbon dioxide. J. Chem. Phys.13:351-62.

The atom and humanity. Science 102:435.

1946

Methods and objectives of the separation of isotopes. Proc. Am. Philos.Soc. 90:30-35.

Atomic energy in international politics. Foreign Policy Rep. 22:82-91.

1947

The thermodynamic properties of isotopic substances. J. Chem. Soc.(London) 1947:562-81.

1948

Oxygen isotopes in nature and in the laboratory. Science 108:489-96.

1950

With C. R. McKinney, J. M. McCrea, S. Epstein, and H. A. Allen.Improvements in mass spectrometers for the measurement ofsmall differences in isotope abundance ratios. Rev. Sci. Instr. 21:724-30.

The structure and chemical composition of Mars. Phys. Rev. 80:295.

1951

With H. A. Lowenstam, S. Epstein, and C. R. McKinney. Measure-ments of paleotemperatures and temperatures of the upper cre-taceous of England, Denmark, and the southeastern United States.Bull. Geol. Soc. Am. 62:399-416.

With S. Epstein, R. Buchsbaum, and H. A. Lowenstam. Carbonate-water isotopic temperature scale. Bull. Geol. Soc. Am. 62:417-26.

Cosmic abundances of the elements and the chemical compositionof the solar system. Am. Sci. 39:590-609.


The origin and development of the earth and other terrestrial plan-ets. Geochim. Cosmochim. Acta 1:209-77.

The social implications of the atomic bomb. Sci. Educ. 30:189-196.

1952

The Planets. New Haven, Conn.: Yale University Press.On the early chemical history of the earth and the origin of life.

Proc. Natl. Acad. Sci. U.S.A. 38:351-63.The origin and development of the earth and other terrestrial plan-

ets: a correction. Geochim. Cosmochim. Acta 2:263-68.Chemical fractionation in the meteorites and the abundance of the

elements. Geochim. Cosmochim. Acta 2:269-82.The abundances of the elements. Phys. Rev. 88:248-52.

1953

With H. Craig. The composition of the stone meteorites and theorigin of the meteorites. Geochim. Cosmochim. Acta 4:36-82.

Chemical evidence regarding the earth’s origin. In XIIth Congress forPure and Applied Chemistry: Plenary Lectures, pp. 188-214.

The deficiencies of elements in meteorites. Mem. Soc. R. Sci. Liege14:481-94.

1955

On the origin of tektites. Proc. Natl. Acad. Sci. U.S.A. 41:27-31.The cosmic abundances of potassium, uranium and thorium and

the heat balances of the earth, the moon and Mars. Proc. Natl.Acad. Sci. U.S.A. 41:127-44.

Distribution of elements in the meteorites and the earth and theorigin of heat in the earth’s core. Ann. Geophys. 11:65-74.

Origin and age of meteorites. Nature 175:321.

1956

Diamonds, meteorites and the origin of the solar system. Astrophys.J. 124:623-37.

With H. E. Suess. Abundances of the elements. Rev. Mod. Phys. 28:53-74.

Regarding the early history of the earth’s atmosphere. Bull. Geol.Soc. Am. 67:1125-28.


The origin and significance of the moon’s surface. Vistas Astron.2:1667-80.

1957

Boundary conditions for theories of the origin of the solar system.Prog. Phys. Chem. Earth 2:46-76.

1958

With H. E. Suess. Abundance of the elements in planets and mete-orites. Handb. Phys. 51:296-323.

The atmospheres of the planets. Handb. Phys. 52.Composition of the moon’s surface. Z. Phys. Chem. (N.F.) 16:346-57.Some observations on educational problems in the United States

with particular reference to mathematics and science. School Sci.Math. March:168-72.

1959

With S. L. Miller. Organic compound synthesis on the primitiveearth. Science 130:245-51.

With S. L. Miller. Origin of life (reply to letter by S. W. Fox). Science130:1622-24.

1960

The origin and nature of the moon. Endeavor 19:87-99.The moon. In Science in Space, a report by the Space Science Board,

National Academy of Sciences, pp. 185-97. Washington, D.C.: NationalAcademy of Sciences.

The planets. In Science in Space, a report by the Space Science Board,National Academy of Sciences, pp. 199-217. Washington, D.C.:National Academy of Sciences.

1961

With N. Kokuku and T. Mayeda. Deuterium content of minerals,rocks and liquid inclusions from rocks. Geochim. Cosmochim. Acta21:247-56.

On possible parent substances for the C2 molecules observed in theAlphonsus crater. Astrophys. J. 134:268-69.

Criticism of Dr. B. Mason’s paper on The Origin of Meteorites. J. Geophys.Res. 66:1988-91.


The dynamic nature of the atmosphere. In The Air We Breathe—AStudy of Man and His Environment, ed. S. M. Farber and R. H. L.Wilson, pp. 9-20. Springfield, Ill.: Charles C. Thomas.

1962

With V. R. Murthy. The time of the formation of the solar systemrelative to nucleosynthesis. Astrophys. J. 135:626-31.

Evidence regarding the origin of the earth. Geochim. Cosmochim. Acta26:1-13.

Origin of the lifelike forms in carbonaceous chondrites. Nature 193:1119-33.

Lifelike forms in meteorites. Science 137:623-28.Origin of tektites. Science 137:746-48.The origin of the moon and its relationship to the origin of the

solar system. In The Moon, ed. Z. Kopal and Z. K. Mikhailov, pp.133-48. New York: Academic Press.

1963

With V. R. Murthy. Isotopic abundance variations in meteorites.Science 140:385-86.

The origin and evolution of the solar system. In Space Science, ed. D.P. LeGalley, pp. 123-68. New York: John Wiley & Sons.

The origin of organic molecules. In Nature of Biological Diversity, ed.J. M. Allen, pp. 1-13. New York: McGraw-Hill.

1964

A review of atomic abundances in chondrites and the origin ofmeteorites. Rev. Geophys. 2:1-34.

With E. C. Anderson and M. W. Rowe. Potassium and aluminum-26contents of three bronzite chondrites. J. Geophys. Res. 69:564-65.

The role of man in space. In Bioastronautics—Fundamental and Prac-tical Problems, vol. 17, ed. W. C. Kaufman, pp. 61-64. North Holly-wood, Calif.: Western Periodicals.

With S. L. Miller. Extraterrestrial sources of organic compoundsand the origin of life (in Russian). In Problems of Evolutionary andTechnical Biochemistry, pp. 357-69. Moscow: Science Press.

1965

With R. L. Heacock, G. P. Kuiper, E. M. Shoemaker, and E. A.


Whitaker. Ranger VII (Part II). Experimenters’ Analyses and In-terpretations, pp. 1-154, Technical Report No. 32-700, Jet Pro-pulsion Lab-NASA.

1966

Chemical evidence relative to the origin of the solar system. Mon.Not. R. Astron. Soc. 131:199-223.

The capture hypothesis of the origin of the moon. In The Earth-Moon System, ed. B. G. Marsden and A. G. W. Cameron, pp. 210-12. New York: Plenum Press.

With R. L. Heacock, G. P. Kuiper, E. M. Shoemaker, and E. A.Whitaker. Rangers 8 and 9 (Part II). Experimenters’ Analysesand Interpretations. Technical Report No. 32-800, Jet PropulsionLab-NASA.

Observations on the Ranger VIII and IX Pictures, pp. 339-61. Tech-nical Report No. 32-800. Jet Propulsion Lab-NASA.

Observations on the Ranger VII Pictures. Technical Report No. 32-700. Jet Propulsion Lab-NASA.

With J. R. Arnold. Biological materials in carbonaceous chondrites.In Biology and the Exploration of Mars, ed. C. S. Pittendrich, W.Vishniac, and J. Pearman, pp. 114-24. Washington, D.C.: NationalAcademy of Sciences.

1967

Study of the Ranger pictures of the moon. Proc. R. Soc. London, Ser.A 296:418-31.

The abundance of the elements with special reference to the ironabundance. (Harold Jeffreys Lecture). J. R. Astron. Soc. 8:23-47.

Parent bodies of the meteorites and the origin of chondrules. Icarus7:350-59.

The origin of the moon. In Mantles of the Earth and Terrestrial Plan-ets, ed. S. K. Runcorn, pp. 251-60. London: John Wiley & Sons.

1968

With K. Marti. Surveyor results and the composition of the moon.Science 161:1030-32.

The origin of some meteorites from the moon. Naturwissenschaften55:49-57.

The problem of elemental abundances. In Origin and Distribution of


the Elements, ed. L. H. Ahrens, pp. 207-53. Oxford: PergamonPress.

Dalton’s influence in chemistry. In John Dalton and the Progress ofScience, ed. D. S. L. Cardwell, pp. 329-44. Manchester: Manches-ter University Press.

1969

Early temperature history of the moon. Science 165:1275.With G. J. F. MacDonald. Geophysics of the moon. Science 5:(5):60-

66.With B. Nagy. Organic geochemical investigations in relation to the

analyses of returned lunar rock samples. In Life Sciences and SpaceResearch VII, pp. 31-45. Amsterdam: North-Holland.

Birth and growth of the oceans. In Oceanography, The Last Frontier,ed. R. C. Vetter, pp.31-44. Forum Series, Voice of America, U.S.Information Agency, Washington, D.C., broadcast for October1969.

1970

With K. Marti and G. W. Lugmair. Solar wind gases, cosmic-rayspallation products and the irradiation history. Science 167:548-50.

With B. Nagy, C. M. Drew, P. B. Hamilton, V. E. Modzeleski, M. E.Murphy, W. M. Scott, and M. Young. Organic compounds in lu-nar samples: pyrolysis products, hydrocarbons, amino acids. Sci-ence 167:770-73.

With B. Nagy, M. Scott, V. E. Modzeleski, L. A. Nagy, M. Drew, W. S.McEwan, J. E. Thomas, and P. B. Hamilton. Carbon compoundsin Apollo 11 lunar samples. Nature 225:1028-32.

With M. E. Murphy, V. E. Modzeleski, B. Nagy, W. M. Scott, M.Young, C. M. Drew, and P. B. Hamilton. Analysis of Apollo 11lunar samples by chromatography and mass spectrometry. Pyroly-sis products, hydrocarbons, sulfur and amino acids. Proceedings ofthe Apollo 11 Lunar Science Conference, vol. 2, pp. 1879-90.

1971

With B. Nagy, J. E. Modzeleski, V. E. Modzeleski, M. A. JabbarMohammed, L. A. Nagy, W. M. Scott, C. M. Drew, J. E. Thomas,


R. Ward, and P. B. Hamilton. Carbon compounds in Apollo 12lunar samples. Nature 232:94-98.

Was the moon originally cold? Science 172:403-5.A review of the structure of the moon. Proc. Am. Philos. Soc. 155:67-

73.

1972

With K. Marti. Lunar basalts. Science 176:117-19.With D. M. Anderson, K. Biemann, L. E. Orgel, J. Oro, T. Owen, G.

P. Shulman, and P. Toulmin III. Mass spectrometric analysis oforganic compounds, water and volatile constituents in the atmo-sphere and surface of mars: the Viking Mars Lander. Icarus 16:111-38.

Abundance of the elements. Ann. N.Y. Acad. Sci. 194:35-44.The origin of the moon and solar system. In The Moon, ed. S. K.

Runcorn and H. C. Urey, pp. 429-40. Dordrecht, Holland: Reidel.Maria Goeppert Mayer (1906-1972). Year Book Am. Philos. Soc. pp.

234-36.Evidence for objects of lunar mass in the early solar system and for

capture as a general process for the origin of satellites. Astrophys.Space Sci. 16:311-23.

1973

Cometary collisions and geological periods. Nature 242:32-33.With V. E. Modzeleski, J. E. Modzeleski, M. A. Jabbar Mohammed,

L. A. Nagy, B. Nagy, W. S. McEwan, and P. B. Hamilton. Carboncompounds in pyrolysates and amino acids in extracts of Apollo14 lunar samples. Nat. Phys. Sci. 242:50-52.

With S. K. Runcorn. A new theory of lunar magnetism. Science 180:636-38.

1974

Evidence for lunar type objects in the early solar system. In High-lights of Astronomy, ed. G. Contopoulos, vol 3, pp. 475-81.

Comment on winning the Nobel Prize. New Sci. 64:10-17.

1975

With S. L. Miller and J. Oro. Origin of organic compounds on theprimitive earth and in meteorites. J. Mol. Evol. 9:59-72.


With H. Alfven. Testimony on the California nuclear initiative. En-ergy 1:105-8.

1977

With J. A. O’Keefe. The deficiency of siderophile elements in themoon. Philos. Trans. R. Soc. London Ser. A 285:569-75.

With J. Oro and S. L. Miller. In Energy Conversion in the Context of theOrigin of Life, ed. R. Buvet et al., pp. 7-19. Amsterdam: North-Holland.

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